Access category enforcement in wireless local area networks

ABSTRACT

The present invention provides a control function in an access point, switch, or like node on a wireless local area network. The control function operates to ensure frames transmitted by a user terminal are transmitted using an appropriate transmission priority scheme. The control function will assist and provide an appropriate priority level to the user terminal. Frames transmitted from the user terminal are passed through the control function, which will analyze priority level information provided in the frames to determine if the frames were transmitted using the appropriate transmission priority scheme. An enforcement action may be taken in response to identifying frames that were not transmitted using the appropriate transmission priority scheme.

This application is a Continuation Application of co-pending U.S. patentapplication Ser. No. 11/482,215, entitled ACCESS CATEGORY ENFORCEMENT INWIRELESS LOCAL AREA NETWORKS, filed Jul. 7, 2006, the disclosure ofwhich is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to communications, and in particular toenforcing access categories in local wireless area networks.

BACKGROUND OF THE INVENTION

Given the ever-increasing desire for mobile communications andcomputing, wireless local area networks (WLANs) have emerged. WLANs nowsupport high-speed wireless communication connections to a network forvarious types of user terminals, including personal computers, computerperipherals, telephones, personal digital assistants, and the like.Although WLAN technology has evolved to a point where there issufficient bandwidth to support voice and other real time sessions,capacity is still finite. As the number of users wanting to communicateincreases, quality of service (QoS) mechanisms are needed to maintaindesired levels of quality.

Most WLAN deployments fall under the IEEE's 802.11 standards. Althoughthe 802.11 products do not currently have a QoS mechanism, the IEEE hasproposed a QoS extension to the basic wireless LAN standards. The QoSextension applies a hybrid coordination function (HCF) to assigncommunication priorities to user terminals that are contending foraccess to a common wireless channel. The QoS mechanism is referred to asenhanced distributed channel access (EDCA).

EDCA now has four access categories, corresponding to distinct prioritylevels for gaining access to a given wireless channel. The four accesscategories are voice, video, best effort, and background. In operation,access categories are assigned to user terminals and applications thatare contending for the wireless channel to transmit or receive frames ofinformation. The access categories may be assigned by a switch or accesspoint of the WLAN backbone network. Theoretically, the user terminalsare supposed to contend for and gain access to the WLAN based on theassigned access categories. User terminals participating in a voicesession are generally given greater and more frequent access to a givenwireless channel than user terminals that are sending emails, whichrequire a priority level corresponding to either a best effort orbackground access category.

Unfortunately, the user terminals may automatically ignore or beconfigured to ignore an assigned access category and use a higherpriority access category than that assigned to the user terminal whencontending for and gaining access to the wireless channel. The switch oraccess point assigning the access categories has no way of ensuring thatthe user terminals are abiding by the assigned access categories. Whenuser terminals do not abide by the relative priory levels for theassigned access categories, QoS goals of the service providers and foreach of the users are not met.

Accordingly, there is a need for a technique to ensure that userterminals are operating in a manner consistent with assigned accesscategories. There is a further need to ensure such operation in a mannerconsistent with existing standards.

SUMMARY OF THE INVENTION

The present invention provides a control function in an access point,switch, or like node on a wireless local area network. The controlfunction operates to ensure frames transmitted by a user terminal aretransmitted using an appropriate transmission priority scheme. Thecontrol function will assist and provide an appropriate priority levelto the user terminal. Frames transmitted from the user terminal arepassed through the control function, which will analyze priority levelinformation provided in the frames to determine if the frames weretransmitted using the appropriate transmission priority scheme. Anenforcement action may be taken in response to identifying frames thatwere not transmitted using the appropriate transmission priority scheme.

Priority levels may be assigned to transmitting frames associated withdifferent applications or types of applications on a given userterminal. The control function may monitor information in the frames toidentify the application or type of application associated with theframe to assist in determining the appropriate priority level for theframe. The particular user terminal from which the frame was transmittedmay be identified using source information in the frames. Different userterminals may have different priority levels assigned to them, even whenthey are sharing a given access channel of the WLAN. In one embodiment,the priority information in the frames is provided in a trafficidentification sub-field within a quality of service field in the frame.Further, the different priority levels may be associated with differenttransmission priority schemes for various access categories, such asbackground, best effort, video, and voice related access categories.

Those skilled in the art will appreciate the scope of the presentinvention and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a block representation of a WLAN communication environmentaccording to one embodiment of the present invention.

FIG. 2 is a chart mapping priority levels with access categoriesaccording to one embodiment of the present invention.

FIG. 3 is a flow diagram illustrating operation of the present inventionaccording to one embodiment.

FIG. 4 represents an IEEE 802.11e frame according to one embodiment ofthe present invention.

FIG. 5 is a block representation of an access point according to oneembodiment of the present invention.

FIG. 6 is a block representation of a switch according to one embodimentof the present invention.

FIG. 7 is a block representation of a user terminal according to oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the invention and illustratethe best mode of practicing the invention. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the invention and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

The present invention provides a technique to ensure that user terminalsand applications operating in a WLAN environment operate in a mannerconsistent with assigned access categories, which correspond to relativepriority levels for communications. In operation, a node in a WLAN willprovide priority information pertaining to priority levels for accessinga wireless channel to a user terminal. Frames transmitted by the userterminal will identify the priority level at which they weretransmitted. Frames transmitted from the user terminals are directedthrough the node that assigned the priority level to the user terminal.The node will determine whether the frame was transmitted using theproper priority level assigned to the user terminal. If the frame istransmitted with the proper priority level, the frame is forwardedtoward its destination. If the frame was not transmitted according tothe proper priority level, the node may take various actions, includingdropping the frame or providing a warning to the user terminal totransmit the frames according to the proper priority level.

Prior to delving into the details of the present invention, an overviewof a WLAN environment 20 is illustrated in FIG. 1. The WLAN environment20 may support wireless communications with various user terminals, suchas a personal digital assistant (PDA) 22, mobile terminal 24, personalcomputer (PC) 26, and mobile terminal 28. Although the user terminalsmay take any form, the following description will use the mobileterminal 24 as an exemplary embodiment. The mobile terminal 24 maysupport Bluetooth and cellular communications in addition to localwireless communications required for WLAN operation. In particular, anEthernet-based switch 32 or the like is operatively coupled to one ormore access points (APs) 30 to form a WLAN backbone network, whereinlocal wireless communications are facilitated between the access points30 and any of the user terminals that are within a local wirelesscommunication range.

Accordingly, frames intended for the mobile terminal 24 may be routedthrough the appropriate switch 32 to an access point 30 that is within alocal wireless communication range of the mobile terminal 24. The accesspoint 30 will then wirelessly transmit the frame to the mobile terminal24 over an appropriate wireless access channel. The mobile terminal 24may initiate delivery of information to a destination endpoint bygaining access to a wireless channel, and when the wireless channel isavailable, wirelessly transmit frames to an available access point 30.The access point 30 will forward the frame to the switch 32, which willfurther forward the frame toward an appropriate destination.

Since numerous mobile terminals 24 may contend for a given wirelesschannel, each mobile terminal 24 applies certain rules and timing to seeif the wireless channel is available. In general, the various mobileterminals 24 that are contending for a given wireless access channelwill check the availability of the wireless channel, and if available,transmit frames to the access point 30 for a certain period of time. Therelative frequency at which the mobile terminals 24 check theavailability of the wireless channel, and the amount of time duringwhich a mobile terminal 24 may transmit frames upon determining that thewireless channel is available, may be proportional to the portion of thewireless channel that is used by the mobile terminal 24.

To control quality of service (QoS), the wireless channel must be sharedamong the various contending mobile terminals 24 in an appropriatemanner. Distribution of a given wireless channel among multiple mobileterminals 24 may be based on priorities associated with the type ofinformation being transmitted in the frames, a subscription levelassociated with the mobile terminal 24, or a combination thereof. Assuch, voice and streaming video sessions may be given priority overinstant messaging, email, and file transfer applications. Further,mobile terminals 24 owned by subscribers who pay a greater subscriptionrate may be given a higher priority, and thus greater opportunity toaccess a given wireless access channel than mobile terminals 24associated with a lower priority. Notably, multiple applications may runon a given mobile terminal 24, and communication sessions associatedwith these different applications may warrant different priority levelsfor the different session on a given mobile terminal 24.

Determination and allocation of priority levels among subscribers andapplications is beyond the scope of the present invention. Those skilledin the art will recognize that priority levels among mobile terminals 24in general and among different applications running on the same ordifferent mobile terminal 24 may be assigned different priority levels.For the present invention, different priority levels may be assigned todifferent mobile terminals 24 as well as different communicationsessions associated with different applications on a given mobileterminal 24. For a mobile terminal 24 or an application running thereon,priority levels associated with corresponding communication sessions areenforced in an efficient and effective manner.

Depending on configuration, different access categories or userpriorities may be selected based on different assignment options. Forexample, priority levels may be assigned based on the address oridentity of the mobile terminal, particular session, or applicationtype. Those skilled in the art will recognize other options. For asession-based assignment, different users, perhaps identified by name,may be assigned to different priority levels. Further, groups of usersmay be assigned to a given priority level. For application-basedassignment, an assignment such as that illustrated in FIG. 2 isapplicable. For example, voice may be assigned to one priority levelwhile file transfer applications may be assigned another priority level.Again, configuration and assignment of the access categories or prioritylevels may be configured in different ways to address a given scenario.

With reference to FIG. 2, a priority mapping schedule is provided for aWLAN communication environment 20 employing local wirelesscommunications according to the IEEE 802.11 standards. In particular,four access categories are defined. These access categories correspondto communication sessions for voice applications, video applications,applications where best effort communications are sufficient, andapplications where background communications are sufficient. Furtherassume that for each access category, two priority levels share theaccess category. Each of the eight priority levels is addressable usinga three-bit word.

In operation, a control function is employed in the access points 30 orthe switch 32, and will assign the priority level associated with anappropriate access category to the mobile terminal 24. The mobileterminal 24 will then transmit frames for a given communication sessionaccording to the assigned priority level. The priority level directlyimpacts the frequency at which the mobile terminal 24 will check todetermine whether the wireless channel is available, and if the wirelesschannel is available, the time during which the mobile terminal 24 willmaintain access of the wireless access channel for transmitting framesfor the given communication session. Again, a given mobile terminal 24may have different priority levels assigned to different communicationssessions for different applications.

A flow diagram is provided in FIG. 3 to illustrate operation of thepresent invention according to one embodiment. Initially, the hybridcontrol function of either the access point 30 or the switch 32 willassign priority levels for one or more applications to each mobileterminal 24 contending for a given wireless access channel (step 100).The hybrid control function will then provide priority informationcorresponding to the assigned priority levels to each of the affectedmobile terminals 24 (step 102).

At this point, the mobile terminals 24 have one or more priority levelscontrolling the mobile terminal's access to the given wireless channel.Different mobile terminals 24 may have different priority levels, anddifferent applications may be assigned different priority levels on agiven mobile terminal 24. Armed with the priority levels, the mobileterminals 24 will begin queuing frames to be transmitted. The mobileterminals 24 may have different queues for different communicationsessions. When different applications or communication sessions areassociated with different priority levels, there will generally be atleast one queue for each priority level. Each frame is created toinclude priority information corresponding to the priority levelsassigned for that particular type of communication session or for themobile terminal 24 in general. All frames associated with a prioritylevel will be transmitted from the mobile terminal 24 and received bythe appropriate access point 30.

Regardless of whether the control function is implemented in the accesspoint 30, the switch 32, or other entity, all frames associated with apriority level are routed through the control function, which willprocess the frames to ensure that the mobile terminal 24 from which theframes were transmitted is abiding by the channel access rulesassociated with the assigned priority level. The control function willmonitor the source information, data, and priority information in theheader of each frame from each mobile terminal 24 (step 104). The sourceinformation of the frame allows the control function to identify themobile terminal 24 from which the frame was transmitted (step 106). Ifnecessary, the data in the frame or other information gathered from theframe header may aid the control function in identifying the applicationassociated with the frame (step 108). Identification of the applicationassociated with the frame is useful when different applications areassigned different priority levels. Upon identifying the mobile terminal24 from which the frame was transmitted and the application associatedwith the frame being transmitted, the control function can determinewhether the priority information included in the frame corresponds tothe priority level assigned to the mobile terminal 24 for the givenapplication (step 110).

Next, the control function will determine if the proper priority levelwas used by the mobile terminal 24 when transmitting the frame based onthe comparison of the priority information provided in the frame and theassigned priority level (step 112). If the proper priority level wasused by the mobile terminal 24 (step 114), the frame is forwarded intraditional fashion (step 116), and the process repeats for eachsuccessive frame received from the mobile terminal 24. If the properpriority level was not used, the control function may take anappropriate enforcement action (step 118). The enforcement action maytake various forms, such as simply dropping the frame, re-sending theassigned priority information to the offending mobile terminal 24,providing an appropriate warning to the offending mobile terminal 24,taking steps to end the communication session with which the frame isassociated, or a combination thereof. Those skilled in the art willrecognize other actions that may be taken when the hybrid controlfunction discovers that a mobile terminal 24 is violating the assignedpriority level.

With reference to FIG. 4, an exemplary IEEE 802.11e frame is illustratedaccording to one embodiment of the present invention. As illustrated,various fields of the frame are illustrated, and the QoS control fieldis expanded to illustrate one possible implementation of the presentinvention. The frame may include the following main fields: framecontrol, duration, source address, access point (AP) address (2),destination address, sequence control, QoS control, frame body, andchecksum. The frame control field generally identifies the type of framebeing transmitted, and in particular may identify management, data, orcontrol frames. For the present invention, the affected frames willgenerally be data frames.

The duration field may specify a period in which the field must bedelivered, wherein frames delivered after the period specified in theduration field are dropped. The source address identifies the address ofthe transmitting endpoint, in this example the address of the mobileterminal 24. The access point address fields may identify the addressesof participating access points 30 involved in the communication path.The destination address field identifies the destination address for theendpoint to which the frame is intended. The frame body field willinclude the data actually being delivered by the frame, and the checksumfield will include some form of checksum to help determine whether ornot there are errors in the transmitted frame.

Notably, the QoS control field may have various sub-fields, including atraffic identifier (TID) sub-field, an end of service (EOSP) sub-field,an acknowledgement (ACK) policy sub-field, a reserved (RSVD) sub-field,and a transmit opportunity duration/queue length subfield. The end ofservice sub-field is not used in this embodiment, and theacknowledgement policy sub-field defines how acknowledgements arehandled in transmitting frames. For example, acknowledgment may beprovided for each frame, for a group of frames, or not at all. Thereserved sub-field is simply reserved for future use, and the transmitopportunity duration queue length sub-field may have two or morepurposes. Transmit opportunity duration may define an amount of timeduring which the mobile terminal 24 intends to maintain access of thewireless access channel, and queue length may provide an indication ofhow many frames are in the queue and ready to be transmitted at themobile terminal 24. Armed with this information, the hybrid controlfunction can dynamically assign priority levels based, at least in part,on the relative needs of the respective mobile terminals 24.

The TID sub-field may be used for implementation of the presentinvention. For example, the TID sub-field may be a four-bit field,wherein the first bit controls whether or not the frame is providingpriority information corresponding to the priority level assigned to themobile terminal 24 or an application provided by the mobile terminal 24.For example, if the first bit is a zero, the following three bits mayprovide priority information corresponding to the priority level used bythe mobile terminal 24 to transmit the frame. These three bits maycorrespond to the priority levels of FIG. 2.

As those skilled in the art will recognize, the mobile terminal 24 mustobtain or have knowledge of the available priority levels and be able tocontrol access to a given local wireless channel based on defined rulescorresponding to the various priority levels. Again, different prioritylevels may define different frequencies at which the given wirelessaccess channel is checked for availability, the duration during whichaccess to the given wireless access channel is maintained once access isobtained, or a combination thereof. Further, the mobile terminal 24 isable to provide the priority information in the TID sub-field orelsewhere in the frame, and function to transmit the frame over thegiven wireless channel according to the priority information provided inthe frame.

If the TID includes the three-bit word corresponding to the prioritylevel used to transmit the frame, the hybrid control function canreadily identify the priority level used to transmit the frame as wellas determine whether the priority level used to transmit the framecorresponds to the priority level that the mobile terminal 24 shouldhave used when transmitting the frame.

Accordingly, the present invention allows different mobile terminals 24,as well as different applications within a given mobile terminal 24, tobe assigned different priority levels associated with different QoSlevels. By having the mobile terminal 24 include priority information ineach frame corresponding to the priority level at which the mobileterminal 24 is actually transmitting the frame, the hybrid controlfunction can monitor each frame to ensure that frames are beingtransmitted according to the appropriate priority levels. Since thehybrid control functions assign the appropriate priority levels to themobile terminals 24, quality of service can be effectively controlledand maintained in an efficient and effective manner. Further, the hybridcontrol function can dynamically reassign priority levels to differentmobile terminals 24 or to different applications in an effort tomaintain appropriate QoS policies. The present invention may be employedfor each available wireless access channel. Further, the priority levelsmay map to corresponding access categories defined in the IEEE 802.11communication standards for WLAN communications.

With reference to FIG. 5, a block representation of an access point 30is illustrated. The access point 30 may include a control system 34having sufficient memory 36 for the requisite software 38 and data 40 tooperate as described above. The software 38 may include the hybridcontrol function for assigning and maintaining priority levelsassociated with the appropriate QoS policies. The control system 34 maybe associated with a wireless interface 42 to facilitate local wirelesscommunications with any number of user terminals, including the mobileterminal 24. The control system 34 may also be associated with a networkinterface 44 to facilitate communications with various entities,including the switch 32 via the WLAN backbone.

A block representation of a switch 32 is illustrated in FIG. 6. Theswitch 32 may include a control system 46 having sufficient memory 48with the requisite software 50 and data 52 to operate as describedabove. Like the access point 30, the switch 32 may provide the controlfunction in the software 50. The control system 46 will be associatedwith at least one network interface 54 to facilitate communications withvarious entities, such as the access points 30 of the WLAN backbone.

The basic architecture of the mobile terminal 24 is represented in FIG.7 and may include a receiver front end 56, a radio frequency transmittersection 58, an antenna 60, a duplexer or switch 62, a baseband processor64, a control system 66, a frequency synthesizer 68, and an interface70. The receiver front end 56 receives information bearing radiofrequency signals from one or more remote transmitters provided by abase station. A low noise amplifier 72 amplifies the signal. A filtercircuit 74 minimizes broadband interference in the received signal,while downconversion and digitization circuitry 76 downconverts thefiltered, received signal to an intermediate or baseband frequencysignal, which is then digitized into one or more digital streams. Thereceiver front end 56 typically uses one or more mixing frequenciesgenerated by the frequency synthesizer 68. The baseband processor 64processes the digitized received signal to extract the information ordata bits conveyed in the received signal. This processing typicallycomprises demodulation, decoding, and error correction operations. Assuch, the baseband processor 64 is generally implemented in one or moredigital signal processors (DSPs).

On the transmit side, the baseband processor 64 receives digitized data,which may represent voice, data, or control information, from thecontrol system 66, which it encodes for transmission. The encoded datais output to the transmitter 58, where it is used by a modulator 78 tomodulate a carrier signal that is at a desired transmit frequency. Poweramplifier circuitry 80 amplifies the modulated carrier signal to a levelappropriate for transmission, and delivers the amplified and modulatedcarrier signal to the antenna 60 through the duplexer or switch 62.

A user may interact with the mobile terminal 24 via the interface 70,which may include interface circuitry 82 associated with a microphone84, a speaker 86, a keypad 88, and a display 90. The interface circuitry82 typically includes analog-to-digital converters, digital-to-analogconverters, amplifiers, and the like. Additionally, it may include avoice encoder/decoder, in which case it may communicate directly withthe baseband processor 64. The microphone 84 will typically convertaudio input, such as the user's voice, into an electrical signal, whichis then digitized and passed directly or indirectly to the basebandprocessor 64. Audio information encoded in the received signal isrecovered by the baseband processor 64, and converted by the interfacecircuitry 82 into an analog signal suitable for driving the speaker 86.The keypad 88 and display 90 enable the user to interact with the mobileterminal 24, input numbers to be dialed, address book information, orthe like, as well as monitor call progress information.

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present invention. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

1. A method of operating a wireless network, comprising: assigning to auser terminal a priority level selected from a plurality of prioritylevels for the user terminal to use when transmitting packets over thewireless network, the priority level corresponding to a quality ofservice (QoS) for packets associated with the user terminal; sendingcontrol information to the user terminal identifying the selectedpriority level; receiving packets from the user terminal, the packetsidentifying a priority level claimed by the user terminal; anddetermining whether the priority level identified in the packetsreceived from the user terminal matches the priority level assigned tothe user terminal.
 2. The method of claim 1, wherein the assigning tothe user terminal a priority level comprises assigning to the userterminal a priority level based on an application currently running onthe user terminal.
 3. The method of claim 2, wherein, when the userterminal is running multiple applications having different communicationneeds, the assigning to the user terminal the priority level comprisesassigning the user terminal multiple priority levels, wherein arespective one of the multiple priority levels is to be used by the userterminal for packets associated with a respective one of the multipleapplications.
 4. The method of claim 1, wherein the priority leveldetermines a frequency of access to a shared transmission channel. 5.The method of claim 1, wherein the priority level determines a frequencyof access to shared wireless communication channels between userterminals and fixed location transceivers.
 6. The method of claim 1,wherein the plurality of priority levels comprises at least two of agroup comprising a background priority level, a best effort prioritylevel, a video priority level, and a voice priority level.
 7. The methodof claim 1, further comprising: forwarding the packets when the prioritylevel identified in the packets matches the priority level assigned tothe user terminal; and taking an enforcement action when the prioritylevel identified in the packets does not match the priority levelassigned to the user terminal.
 8. The method of claim 7, wherein theenforcement action comprises at least one of a group comprising droppingthe packets, providing a warning message to the user terminal, resendingthe control information to the user terminal, and ending a sessionassociated with the packets.
 9. The method of claim 1, wherein thepackets are configured as a plurality of frames, each of the pluralityof frames having at least one field identifying a priority levelassociated with the frame.
 10. The method of claim 1, wherein thewireless network is a wireless local area network.